1. Field of Invention
The present invention relates in general to an improved system and method for developing, displaying, and transmitting three-dimensional images of a target scene over a limited bandwidth transmission medium. More specifically, the invention concerns a LADAR system and method for producing and processing light signals to be representative of a three-dimensional target scene, and transmitting the processed signals over limited bandwidth data links for displaying a segment of the scene at a remote site.
2. Description of Related Art
A need of great importance in military and some civilian operations is the ability to quickly detect and identify objects, frequently referred to as "targets" in a background or scene. A common problem in military operations, for example, is to detect and identify targets in the form of armor, such as tanks, vehicles, guns, and similar items which have been camouflaged or which are operating at night or in foggy weather. It is important in many instances to be able to distinguish reliably between enemy armor and friendly armor. It is important that such information be available not only on-site but also at various command levels, generally at remote locations. It is also critical that the information be accurate and promptly transmitted. All too frequently, critical decisions must be made on-site without adequate knowledge or review by command personnel.
Presently, transmission of target acquisition data from a field to a remote command station is believed to be limited to voice, text, or icon representations of information that a human operator has previously distilled. That is, before sensor-gathered target acquisition data is transmitted, an on-site human operator must process the sensor-gathered target acquisition data and manually enter the processed data into a system. For example, in current implementations, voice is used to transmit sensor-gathered target acquisition data over a Single Channel Ground and Air Radio System (SINCGARS). To effect such a transmission, a human operator at a sensor site processes sensor-gathered target acquisition data by visually identifying targets. This on-site human operator typically then transmits the processed sensor-gathered target acquisition data by voice. At the receiving end, a remote human operator interprets the transmitted data and represents that data on a paper map or plastic overlay. Additionally, the remote operator utilizes the transmitted data to classify the detected target as friend or foe. Consequently, when a target is detected, a receiving combat platform and/or command and control node must make strategic decisions based on target acquisition data that has been processed by an on-site human operator, transmitted using voice format, interpreted by a receiving remote human operator, and displayed on paper maps and plastic overlays.
Additionally, current systems for on-site sensing use sensors which produce raw data in a format that cannot be efficiently transmitted to other platforms at the limited bandwidth of existing and planned SINCGARS communications equipment. In that regard, high quality imaging sensors produce very large amounts of digital data. For example, a typical video transmission consisting of 512.times.512 pixels (each pixel comprising 8 bits of grey scale or color) at a 30 Hz frame rate yields approximately 7.9 megabytes of data per second (512.times.512.times.30). But SINCGARS typically are characterized as having a bandwidth of only 16 kilobit/sec. (projected) and 4.8 kilobit/sec. (existing). Attempting to transmit video over the 16 kilobit/sec. projected and the 4.8 kilobit/sec. existing military SINCGARS network poses bandwidth and/or speed problems for many applications.
Another known approach to overcome SINCGARS limited bandwidth restriction is to perform target classification at the sensor site (i.e., on-site) and transmit only the results of the target classification. In this instance, target classification is performed by an on-site computer employing an automatic target recognition algorithm wherein sensor-gathered target acquisition data is characterized using computer models. For example, a LADAR ("LAser Detection And Ranging") system may be employed to scan the scene with a laser beam. A sensor detects reflected beams characteristic of the scanned target and generates target acquisition data. Once the sensor-gathered target acquisition data is received, the computer algorithms classify the target. The result of this target classification is then transmitted over communication links to a combat platform or command and control node (i.e., a remote site), where decision-makers determine whether to engage the detected target. By reducing the amount of data requiring transmission, this approach functions with limited bandwidth capability. However, this approach suffers from the problem that battlefield decision-makers are usually reluctant to attack targets classified solely by a computer.
In summary, within the limited bandwidth environment, users currently are faced with two less than desired options: (1) attempt to transmit complete video images resulting in saturated data links or reduced-quality imagery, or (2) allow a remote sensor and computer to perform target classification and transmit text results of the classification, forcing a user to take actions based solely on the results of remote equipment.